Hi,
is it possible to call a c-function during the initalization of the startup-file? Could you give me one simple example?
; Reset Handler EXPORT Reset_Handler Reset_Handler ; open lowlevelinit c-function ; IMPORT LowLevelInit ; Setup Power Management Controller (PMC) -------------------------------------- IF :DEF:NO_PMC_INIT ELSE IF PMC_SETUP != 0 LDR R0, =PMC_BASE
Do you know any important things writing this init-function? How do the startup-file know the place / the c-file , where the function is declared?
best regards Alan
It is perfectly fine using C in your start up code, provided that you follow some guidelines:
1. All (C-)functions that are called from startup code must be located in a root region (load address == exec address)
Scatter loading has not been taken place, yet.
2. The supervisor stack has been set up.
We need some stack for local variables, etc. You never know what the compiler does exactly.
3. No functions from the C library must be called directly or indirectly.
The C library initialization has not been executed.
4. Know what you are doing.
Some startup tasks might be easier to implement in C, others are not.
Regards Marcus http://www.doulos.com/arm/
excellent comments, Marcus. If the OP is indeed busy with some EmbeddedArtists code as it looks like, then the LowLevelInit function certainly uses C library function calls, as far as I can recall!
Thanks, Tamir. One more:
6. Don't rely on initial values of global variables
What happened to 5?
Left as exercise :-) We are a training company you know.
Tamir was expected to have written #5
the lowlevelinit function use c-level functions (start main oscillator and pll for example).
for example:
//turn on main oscillator AT91C_BASE_PMC->PMC_MOR = AT91C_CKGR_MOSCEN; while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MOSCS));
best regards Scott
what about "console" initialization...?
what about "console" initialization...? what do you mean by console init?
can you post the function that is called?
my lowlevelinit function is:
void LowLevelInit(void) { // turn on the main oscillator // AT91C_BASE_PMC->PMC_MOR = AT91C_CKGR_MOSCEN; while (!(AT91C_BASE_PMC->PMC_SR & AT91C_PMC_MOSCS)); // enable PLLA for 198.656Mhz AT91C_BASE_PMC->PMC_PLLAR = 0x2060BF09; // Enable the clocks to all the on-chip peripherals AT91C_BASE_PMC->PMC_PCER = 0xed2fff9f; // set Master Clock divide by 2. AT91C_BASE_PMC->PMC_MCKR = AT91C_PMC_MDIV_1; // first switch MCK to slow clock AT91C_BASE_PMC->PMC_MCKR = AT91C_PMC_CSS_PLLA_CLK | AT91C_PMC_MDIV_2; }
Scott, You said that your processor is "not running properly". Again - what does that mean exactly?
If I use the original startup code, and try to debug, then the processor is starting in supervisor mode and I'm not able to see my c-code within the disassembly. After a short moment, the debugger will stop (the last address is 0xFFFF... whithin the registers)...
If I comment the main oscillator startup and the pll init then the programm is running and I can debug the code.
maybe your PLL settings are bad?
that's the whole setup code for both plls and the main oscillator.
I don't use the pll b (and I also tested the code without the pll b). Pll_a (divider is 13 and multipler is 141), the main oscillator is 18.432 MHz -> I get a nearly 200 MHz system clock. The master-clock (bus-block) is the half of the 200MHz clock.
So I think all settings must be ok.
; Setup Power Management Controller (PMC) -------------------------------------- IF :DEF:NO_PMC_INIT ELSE IF PMC_SETUP != 0 LDR R0, =PMC_BASE ; System Clock Enable LDR R1, =PMC_SCER_Val STR R1, [R0, #PMC_SCER_OFS] ; Peripheral Clock Enable LDR R1, =PMC_PCER_Val STR R1, [R0, #PMC_PCER_OFS] ; Setup Main Oscillator IF (CKGR_MOR_Val:AND:PMC_MOSCEN) != 0 LDR R1, =CKGR_MOR_Val STR R1, [R0, #CKGR_MOR_OFS] ; Wait until Main Oscillator is stabilized MOSCS_Loop LDR R2, [R0, #PMC_SR_OFS] ANDS R2, R2, #PMC_MOSCS BEQ MOSCS_Loop ENDIF ; Setup the PLL A IF (CKGR_PLLAR_Val:AND:PMC_MUL) != 0 LDR R1, =CKGR_PLLAR_Val STR R1, [R0, #CKGR_PLLAR_OFS] ; Wait until PLL A is stabilized PLLA_Loop LDR R2, [R0, #PMC_SR_OFS] ANDS R2, R2, #PMC_LOCKA BEQ PLLA_Loop ENDIF ; Setup the PLL B IF (CKGR_PLLBR_Val:AND:PMC_MUL) != 0 LDR R1, =CKGR_PLLBR_Val STR R1, [R0, #CKGR_PLLBR_OFS] ; Wait until PLL B is stabilized PLLB_Loop LDR R2, [R0, #PMC_SR_OFS] ANDS R2, R2, #PMC_LOCKB BEQ PLLB_Loop ENDIF ; Setup the Master Clock and the Processor Clock LDR R1, =PMC_MCKR_Val LDR R2, =(PMC_MCKR_Val:AND:0x0000031C) ; Program MDIV and PRES fields only STR R2, [R0, #PMC_MCKR_OFS] ; Wait until Main Master Clock is ready MCKR_Loop1 LDR R2, [R0, #PMC_SR_OFS] ANDS R2, R2, #PMC_MCKRDY BEQ MCKR_Loop1 ; Program MDIV and PRES with CSS STR R1, [R0, #PMC_MCKR_OFS] ; Wait until Main Master Clock is ready MCKR_Loop2 LDR R2, [R0, #PMC_SR_OFS] ANDS R2, R2, #PMC_MCKRDY BEQ MCKR_Loop2 ; Setup Programmable Clock Register 0 LDR R1, =PMC_PCK0_Val STR R1, [R0, #PMC_PCK0_OFS] ; Setup Programmable Clock Register 1 LDR R1, =PMC_PCK1_Val STR R1, [R0, #PMC_PCK1_OFS] ; Setup Programmable Clock Register 2 LDR R1, =PMC_PCK2_Val STR R1, [R0, #PMC_PCK2_OFS] ; Setup Programmable Clock Register 3 LDR R1, =PMC_PCK3_Val STR R1, [R0, #PMC_PCK3_OFS] ENDIF ENDIF ; of IF :DEF:NO_PMC_INIT